Two-way high-frequency signaling



Dec. 16, 1924. 1,519,626

H. W. N|CHOL$ TWO'WAY HIGH FREQUENCY SIGNALING Filed Sept. 26, 1919 Arr3 Patented Dec. 16, 1924.

UNITED STATES PATENT oFl-lca.

HAROLDW. NICHOLS, 0F MAPLEWOOD, NEW JERSEY, ASSIGNOR 'IO WESTERN ELEC-TRIO COMPANY, INCORPORATED, OF NEW YORK, N. Y., A. CORPORATION OF NEWYORK.

TWO-WAY HIGH-FREQUENCY SIGNALING.

Application filed September 28, 1919. Serial No. 826,498.

To all whom it may concern:

Be it known that I, Hnnow W. N narrow, a citizen of the United Statesresi'dln at Maplewood, in the countyof lissex', tate of New Jersey, haveinvented certaln new and useful Improvements in Two-Way High-FrequencySignaling, of WhlCh the following is a full, clear, concise, and exactdescription.

The present invention relates to the twoway transmission of currents forsignallng or other purposes, and particularly to the two-waytransmission of signals by means of high frequency currents or waves.

By two-way transmission is meant, for the purpose of the presentspecification, transmission between two separated stations wlthsubstantially equal facility in each direction, so that if the signalingsystem be a high frequency telephone system, for 1nstance, conversationmay be carried on between stations, as in the case of the ordinary wiretelephone systems employing only voice frequencies.

By high frequency is meant a frequency above the limits of audibility orat least,

near the limit of audibility as distinguished from frequencies that areeasily heard such as those comprised in the voice frequency range. Thehigh frequency currents or waves herein referred to are commonly calledcarrier currents or waves as distinguished from the low frequencysignaling currents or waves by WhlCh the carrier wave is modulated.

Two-way transmission by means of high.

frequency currents or waves has always presented a difiiculty, in thatthe high frequency currents or waves must be acted upon by the signalwaves, such as volce waves, in the process of transmitting, and thereceived high frequency waves must again be acted upon in a differentmanner in order to render the signal currents or waves discernible. Ithas been the practice heretofore, to provide one set of apparatus fortransmitting, including a modulator for transforming low fre uencycurrentsv into variations of the high frequency currents or Waves and aseparate set of apparatus for receiving, including a detector, ordemodulator, for transformin the high frequency variations into lowrequency currents to be received. It has been the practice in radiosystems for two-way communication to provide switching means forassociating one or the other sets of apparatus with the antennaeaccording as the user wishes to transmit or to listen. Inwiretransmission systems for signaling by high frequency, it has beencustomary instead of providing switches for the purpose stated, toemploy a balancing circuit so that the receiver is unaffected by thelocal companion transmitter but is affected by the distant transmitter.In word-to-word conversation, the switching back and forth betweentransmitter and receiver and the line or antennae is very cumbersome andunsatisfactory. The party who is transmitting does not hear either hisown or the distant partys voice in his receiver, and it is im- POSSIblGfor the receiving party to interrupt the transmission for any purposesuch as to have a word repeated. The balancing circuit which is commonlyused on wire lines for high frequency transmission has the disadvantageof not permitting the transmitting party to-hear his voice in his ownreceiver, which is not essential, but is convenient as an indicationthat the transmitter is working properly. Practical tests have shownthat the balancing circuit for twowa signaling, such as is used onlines, is di cult to adapt to radio transmission, and the method ofswitching with its inherent disadvantalges has been quite generallyadopted. 11 addition to the objections just pointed out, the necessityof providing a set of transmitting apparatus and a separate set ofreceiving apparatus adds to the expense anddbulk of the two-way systemsheretofore use An object of the present invention is to dispense withswitching arrangements and balancing circuits in a two-way high frequency signaling system and to employ a single set of apparatus for bothtransmitting and receiving.

A feature of the invention is the use of the same discharge device in anovel manner for both transmitting and receiving.

A further feature of the invention is the use of a discharge device as athree-element device for amplifying or modulating and as a two-elementdevice for detecting.

A still further feature of the invention is the use of a dischargedevice for partially detecting the signal being transmitted so that itmay be heard in the-local receiver, and for detecting the signal beingreceived so that it may be heard in the same receiver.

Other features of the invention will appear from the followingdescription of the embodiment of the invention which is illustrated inthe drawings, in which Figs. 1and 2 illustrate applications of theinvention to a radio telephone system. Fig. 3 illustrates the inventionas a lied to a carrier current transmission line, 1g. 4.- illustrates aslightly diflerent circuit arrangement and Fig. 5 discloses amodification which may be emloyed in any of the systems of the othergures.

Telephone systems are illustrated and below described, not because theinvention is limited to telephony but because telephony is the morehighly developed type of signaling, and in view of prior art, it will beobvious how to substitute, in the systems herein described, a source ofhigh frequency waves controlled in accordance with telegraph or othersignals or for other purposes in the place of the source of highfrequency waves modulated in accordance with the voice.

In Fig. 1, speech-modulated radio frequency waves from the modulator Mare impressed upon the antenna 1 through the amplifier A as is the usualpractice. The modulator M, which may be of any suitable type, is shownas a single thermionic tube having its input circuit supplied with radiofrequency waves from the generator, diagrammatically indicated at 2.This generator may as a thermionic oscillator, an arc generator or othersource for furnishing a continuous wave of radio frequency, and is showncoupled to the modulator input at 3. Also coupled to the input of themodulator M is a circuit containing the microphone 4 and battery 5. Whenspeech is directed against the microphone 4, potential variationscorresponding to the voice vibrations are produced in the input circuitof the modulator M, and by the well-known action of the modulator, thesecurrents produce corresponding variations in the amplitude of the wavefrom source 2, that is transmitted by the modulator. The modulated radiofrequency wave is amplified at A and is impressed upon the transmittingantenna 1. The amplifier A is of the well-known thermionic type but itsoutput circuit in addition to being coupled to the transmitting antenna1, contains a receiver 6 preferably in series with the source 7 of thespace current. Receiver 6 is an audible-frequency receiver and ispreferably shunted by a'condenser 8 to by-pass the high frequencycurrent. As

shown, the condenser shunts both the receiver 6 and the battery 7. It isan experimental fact that with the voltages of space be of any suitabletype such' current battery 7 and grid battery 9 suitably adjusted, thelow frequency component of the modulated high frequency wave is heard inreceiver 6. In the circuit, as shown,

for instance, speech directed against the microphone 4 is heard inreceiver 6 due probably to a certain rectifying or detecting property ofthe amplifier A. Incoming signal modulated waves intercepted by theantenna 1, produce corresponding voltage variations which aresuperimposed on the circuit of amplifier A, including the filament 10and the anode or plate 11, and generally termed the output circuit. Theamplifier A then acts similarly to a two-electrode detector enabling theaudio frequency modulation component to be heard in receiver 6. Theradio-frequency wave from source 2, although a certain amount of it isbeing transmitted through the amplifier A to the antenna 1 continuously,as explained, has no effect upon the receiver 6, so long as it. isunmodulated, and its presence in the out-- put circuit of amplifier Adoes not interfere with the reception of incoming signals from antenna 1by means of receiver 6, as de' scribed. The operator therefore, intalking into transmitter 1 hears his own voice at receiver 6, althoughreceiver 6 is in position to receive signals from the distant stationwithout the necessity of operating any switching device or the like.

WVith the circuit arrangement as shown in Fig. 1 there is a possibilityof some of the voice frequency currents from the microphone circuitbeing transmitted directly as voice frequency currents through themodulator M and amplifier A to the receiver 6, instead of being entirelyrepresented as high frequency modulations. This might tend to make thesignals heard in the receiver unduly loud during the time that speech isbeing transmitted, or might confuse the sig nal that is heard in thereceiver6 under these circumstances. To prevent the passage of currentsof voice frequency, the cir' cuit of Fig. 2 may be employed, in whichthe numeral 12 indicates most of the circuit of the oscillator andmodulator of Fig. 1, as will be clear from a comparison of the twofigures. Between the modulator and the amplifier A there is inserted ahigh-pass filter 13, designed (preferably in the manner described in theU. S. patent to G. A. Campbell No. 1,227,113, granted May 22, 1917) tosuppress practically completely all currents of the voice frequencyrange but to transmit freely to the amplifier A the modulated radiofrequency currents. Voice currents, due to speech directed against themicrophone 4:, will still be heard in the receiver 6, however, due tothe detecting action of the amplifier A.

In Fig. 3, a simple two-way two-station, high frequency carriertelephone system for a wire line is indicated. The line 15 may bemultiplexed for any desired number of independent conversations byapplying other high frequency sets similar to those shown, but thesystem will be understood from considering merel two such stations, Sand S which may assumed to be arranged for inter-communication. However,taps 20 and 21 are shown to indicate that other-stations may beconnected to the line 15 as may be desired. The microphone 4, modulatorM, amplifier A and receiver 6 may be the same as those alreadydescribed. The nerator 2 of this fi are preferably has a requency ofseveral t ousand cycles, but is preferably not of such frequency aswould ordinarily be em loyed for radio transmission. The ampli er A iscoupled by means of coils 17 to the line branch 18, which includes bandfilter 19 of the type described in the Campbell patent above referredto, capable of transmitting only a limited range of frequencies. If onlythe two stations S and S are present on line 15, no filter 19 isnecessary but if the line is multiplexed for independent conversationsthere will be a plurality of high frequencies set apart for thedifferent communication channels as is well understood by those skilledin the art, and it is necessary to connect each stat-ion to the linethrough a filter such as 19 which will pass only the frequenciesintended for that station. It should be noted that no balancing circuitsare needed for the high frequency line 15 in the present system and thatone filter 19 serves to transmit all the frequencies with which stationS is concerned, in

both directions between the line 15 and station S The same is, ofcourse, true of the filter at station S,., which filter is in everyrespect similar to that at statlon S The operation of the system of Fig.3 is similar to that described in connection with Fig. 1. Modulated highfrequency currents from the modulator M are amplified at A and impressedon the line 15. During this transmission of the modulated high-frequencycurrent, voice current or the other signal current that may be employedto modulate the high frequency current, appears as detected current atthe receiver 6 and may be heard. The modulated current is also impressedon line 15, is selectively received through filter 19 at station S andproduces detected signal indications in the receiver 6 at that station.In the same manner speech or other signals are transmitted from stationS to station" 8,, the apparatus diagrammatically indicated at station Sbeing entirely similar to that shown more in detail at station S,. It isunderstood that a filter such as 13 may be inserted at the correspondingpoint in the circuit of Fig. 3 for the same purpose that is explained inFig. 2. It may be noted, however, that less attention need be. iven toreducing the loud- I:

ness of the 'soun in receiver 6 in the s stem of Fig. 3 during thetransmission than in the case of the system of Fig. 1, since the ratiobetween the energy transmitted and that received is much smaller in awire transmission s stem than in a radio system.

In ig. 4 the speech modulated carrier wave is impressed upon thetransmission circuit without the intervention of amplifier A, as shownin the preceding res, between the modulator M and tIIHlSIlLlSSlOIlcircuit.

Referring now to Fig. 5, there is shown the amplifier A such as might beemployed in any of the circuits that have been described. Instead of thereceiver 6 being inserted directly in the circuit of the battery 7,however, the primary of a transformer 22, suitable for speechfrequencies, is inserted at the point occupied byreceiver 6 in the otherfigures, and the secondary of the transformer 22 is connected to anamplifier 23 in the output of which the receiver 6 is placed. The actionas regards amplifier A 1s the same as that hereinbefore described, butby the use of the amplifier 23, as is obvious,.stronger signals areobtained in the receiver 6.

In cases where it may not be necessary to use the amplifier A forincreasing the ener of the transmitted wave, the receiver 6 or t etransformer 22 of Fi 5 may be inserted in 'the output circuit of themodulator M as derstood that the invention is not limited to theparticular arrangements that have been illustrated and described for thepur-' pose of disclosing the features and ob'ects of the invention butonly by the scope o the appended claims.

What is claimed is:

1. In a two-way signaling system, a threeelectrode discharge device forboth transmitting and receiving signals, a. circuit connected betweenone electrode and a second electrode of said device for controlling thedevice as a. three-electrode device in transmitting and a circuitconnected between said first-mentioned electrode and a third electrodeof said device for controlling said device exclusive of said firstmentioned electrode as a two-electrode device in receiving.

2. In a two-way signalin circuit, a discharge device having a cat ode,an anode and an impedance controlling element, for

both transmitting and receiving signals, circuits for impressing energyupon said cathode and impedance controlling element for transmitting,and upon said cathode and anode exclusively of said impedancecontrolling element for receiving, and a receiver associated with saidcathode and anode.

A discharge device having an input circuit and an output circuit, asource of sending Waves connected to said input circuit,

a circuit for received waves connected tosaid output circuit, and areceiver. connected to said output circuit and actuated by the energy ofsaid received Waves.

4. In a two-way signaling circuit, a discharge device having a cathodeand an anode and a control element, a source of signalin waves fortransmission associated with said cathode and control element, a two-waysignal-transmission circuit associated with said cathode and anode, anda receiver associated with said cathode and anode for separately andindependently responding to waves transmitted from said source and Wavesreceived from said transmission circuit.

5. A discharge device having a circuit including a discharge'space, acontrol circuit for influencing the impedance of said discharge space,and a source of transmitting signal waves associated with said controlcircuit, a circuit for impressing received signal waves upon said firstmentioned circuit exclusively of said control circuit, and areceiver-associated with said first mentioned circuit.

6. In a two-Way signaling circuit, a discharge device having an inputcircuit and an output circuit including a space current source, a signaltransmission circuit associated with said device, means associated withsaid input circuit for controlling the current in said output circuitfor transmitting signals, and means associated with said transmissioncircuit for controlling the current in said output circuit exclusivelyof said input circuit for receiving signals.

7. In a two-way signaling system, a discharge device having input andoutput circuits, a. circuit for operating on said input circuit tocontrol transmission of signals, and a circuit for operating on saidoutput circuit exclusively of said input circuit to control reception ofsignals.

8. In a two-way signaling system, a discharge device having input andoutput circuits, a circuit for-operating on said input circuit tocontrol transmission of signals, a circuit for operating only on saidoutput circuit to control reception of signals, and a receiver connectedWithsaid output circuit.

9. In a two-way signaling system, a transmission circuit, a dischargedevice having an input circuit and an output circuit, a

transmitter and a receiver associated with saiddevice, means fortransmitting signals I 10. In a two-way signaling system, a dis" chargedevice having input and output circuits, a circuit for impressingmodulated high frequency currents upon said, input circuit, a circuitfor impressing modulated iigh frequency-currents upon said outputcircuit, and a low frequency receiver associated with said outputcircuit for receiving a modulation com onent of either of said modulatedhigh requency currents independently of the other. a

11. A discharge device having a control circuit and a power .circuit, asource of variable currents associated with said control circuit forcontrolling said power, circuit to transmit variable currents, a circuitfor impressing other variable currents upon said power circuit, and areceiver connected to said power circuit for responding to the detectingaction of said discharge device upon bothof said kinds of currents,respectively.

12. A discharge device having a circuit including a discharge space andan element for controlling said circuit by modifying a characteristic ofsaid discharge space, a receiver associated with said circuit, a sourceof variable currents associated wth said derice for acting upon saidelementfito 'a-tfect said receiverby controlling said circuit, and asource of currents for acting upon said circuit to affect said receiverthrough the medium of said discharge space exclusive of said element.

13. A discharge device, a circuit including elements of said device anda signal indicator, a control circuit including another element of saiddevice for controlling said circuit including said indicator, a sourceof waves associated wit-h said control circuit for controlling saidfirst mentioned circuit to affect said indicator; and a circuit forreacting upon said first mentioned circuit to control said indicatorthrough the medium of said discharge device.

l4. A source of outgoing variable highfrequency waves, a source ofincoming variable high-frequency waves, a receiver for waves from bothsources, a discharge device for modifying said variable high frequencywaves to render them capable of'afi'ectiug said receiver, circuitsoperatively associated with both of said sources, said device having anelectrode included in both of said circuits, and an electroderespectively connected to each of said circuits whereby said device iscontrolled to affect said receiver in accordance with the transmittedand the received waves, respectively.

15. A discharge device having a source for giving off electrons, ananode and a control element, a control circuit including said source ofelectrons and said control element, an anode circuit including saidsource of electrons and said anode, a receiver asso; ciated with saidanode circuit, means for affecting said receiver comprising a source ofwaves for acting upon said control circuit, and other means forcontrolling said receiver comprising a source of waves for acting uponsaid anode circuit independently of said first mentioned source ofwaves.

16. A discharge device for transmitting and receiving high frequencywaves modulated by signal currents having a cathode and an anode, and acontrol element, a source of transmitting signal waves connected to itscathode and control element, a signaling circuit connected to .itscathode and anode. a condenser in the circuit of said cathode and anode,and a signal receiver in shunt of said condenser for receiving signalcurrents due to the action'of said device on the waves from said source,and for receiving other signals due to the action of said device on thewaves in said signaling circuit.

17 In a two-way circuit for transmitting signals by means of highfrequency currents, a l1ne connecting separated stations, means at eachstation for impressing modulated high frequency currents on said lineand for receiving modulated high frequency currents from said lineincluding a discharge device, a source of transmitting high frequencywaves therefor, and a signal receiver in the circuit of said dischargedevice for indicating signals impressed on said line, and received from.said line. Y

18. A two-wlay circuit for transmitting signals by means of highfrequency currents oomprlsing a line for transmitting high frequencycurrents, a source of high frequency currents for said line and a sourceof signaling currents for modifying said high. frequency currents,- adischarge device having an input circuit operatively associated withsaid sources and its output circuit operatively associated with saidline, and a receiver for signaling currents connected to said outputcircuit.

19. In a two-way signaling system, a high frequency. transmissioncircuit, a discharge device having an output circuit operativelyassociated with said transmission circuit and an input circuit, meansincluding said input circuit for transmitting high frequency currents tosaid output circuit, other means including said transmission circuit fortrans mitting high frequency currents to said output circuit to theexclusion of said input circuit, said discharge device acting to saidhigh frequency currents to low frequency currents, and a low frequenreceiver connected to said output-circuit.

20. A signal transmission circuit for transmitting and receivingsignals, a source of slgnahng currents for said circuit, a dis chargedevice for transmitting currents from said source to said circuit, anamplifier havmg its input circuit connected to said discharge device andhaving a receiver in its output circuit for registering both transmittedand received signals.

21. In a two-way signaling system, an electron discharge device hiavinga dischar spare and a cathode, an anode and a grid or impedance controlelement, means for utilizing the grid to control the characteristics ofsaid discharge space to transmit signal waves, and means to control thecharacteristics of said discharge space solely by potentials applied tosaid anode and cathode for receiving signals.

22. In a two-way signaling system, a twoway transmission circuit, aone-way repeating device of the audion type associated therewith havinggrid and anode circuits, a

source of signaling waves for transmission (onnectcd to the gridcircuit, said grid circuit and transmission circuit being associatedonly through the medium of said device, and a signal receiver in theanode circuit for responding to both the signals transmitted from saidsource and the signals received over said transmission circuit.

23. In a two-way signaling system, a twoway transmission circuit, athree-electrode discharge device having an impedance-control or gridcircuit and an anode circuit a source of transmitting waves associatedw1th said grid circuit, said device and circuits being arranged totransfer waves between said grid circuit and said transmission circuitonly in the direction from said grid circuit to said anode circuit and areceiver connected to said anode circuit for responding both to thepresence of transmitting waves in said anode circuit from said sourceand to waves in said anode circuit impressed from said transmissioncircuit.

24. In a. two-way wave signaling system, an electron discharge devicehaving a cathode, an anode and a grid or impedancecontrol element, agrid circuit and an anode circuit, a. two-way wave-transmission circuitconnected to said anode circuit, means for impressing waves on saidgrid.- circuit to be transmitted, said transmission circuit beingarranged to impress received waves on said anode circuit exclusively ofsaid grid circuit, and a signal receiver connected to said anode circuitfor responding to transmitted and received signals.

25. In a two-way repeatin s stem, a discharge device having a ca 0 e, ananode and a grid or impedance controllin element, a receiver connectedto said ano e and cathode, means for applying waves representing signalsbetween said cathode and grid for actuating said receiver, and othermeans for independently applying waves representing other signalsbetween said cathode and anode for actuating said receiver.

26. In a two-way high frequency signaling system, a three-electrodedischarge device for both transmitting and receiving, means for suplying high frequency currents modified y signal currents to control saiddevice as athree-electrode device for transmission, means for supplyinghigh frequency current modified by signal currents to control saiddevice independently of said first mentioned means as a two-electrodedevice for reception, and a receiver for signal currents associated withsaid device.

27. In a two-way high frequency signaling s stem, a three-electrodedischarge device or both, transmitting and receiving, an input circuitand an output circuit for said device, a source of modulated hi hfrequency currents of variable amplitu e associated with said inputcircuit, a transmission circuit for supplying variable amplitude highfrequency currents to said output circuit for operating said device as atwoelectrode device, and a receiver for low frequency currents ofvariable amplitude as sociated with said output circuit.

28. In a two-way high frequency signaling system, a transmissioncircuit, a threeelectrode discharge device for both transmitting andreceiving, an input circuit and an output circuit for said device, asource of high frequency currents modified in accordance with signalcurrents of variable amplitude coupled to said input circuit to controlsaid device as a three-electrode device for transmission, a source ofhigh freuency currents modified in accordance with signal currents ofvarying amplitude coupled to said output circuit to control said deviceas a two-electrode device for reception, and a receiver for signalcurrents associated with said output circuit.

29. A two-way circuit for transmitting signals comprising a highfrequency transsame frequency modulated in accordance with variableamplitude signal currents to said output circuit, said discharge deviceacting to change said carrier currents to low frequency currents and alow frequency receiver associated with said output circuit.

30.,A two-way circuit for, transmitting signals comprising a highfrequency transmission circuit, a dischar e device having an outputcircuit associate with said transmission circuit, an input circuittherefor, means for supplying carrier currents modulated in accordancewith variable amplitude signal currents to said input circult, and othermeans including said transmission circuit for supplying carrier currentsof the same'frequency modulated in accordance with variable amplitudesignal currents to said output circuit, said discharge device acting asa three-electrode discharge device for transmission and as atwo-electrode discharge device for reception to change said carriercurrents to low frequency currents, and a low frequency receiverconnected to said output circuit.

31. A two-way circuit for-transmitting signals comprising a transmissioncircuit, a source of high frequency currents for said circuit and asource of signal currents for modifying said high frequency currents, athree-element discharge device having an input circuit operativelyassociated with said sources to be controlled thereby as a three-elementdevice for transmitting and an output circuit associated with saidtransmission circuit for operating said device as a two-element device forreceiving, and a a receiver for signal currents connected to said outputcircuit. 0

In witness whereof, I hereunto subscribe my name this 25th day ofSeptember A. D., 1919.

HAROLD W. NICHOLS.

